1. Field of the Invention
The present invention relates to seals and more particularly to seals made of compacted knitted wire with a V-shaped cross section having protrusions for preventing complete nesting of the seals during packaging and shipping. Specifically, a seal of the type described in U.S. Pat. No. 4,683,010, which is hereby incorporated by reference in its entirety, has been modified and improved upon.
2. State of the Art
It is generally known that seals and/or gaskets which are suitable for some applications can be made from compacted knitted-wire elements. Seals and gaskets have been produced comprising elements which are made by knitting wire to form a sheet or a knitted tube, rolling the sheet or tube to form a roll or a ring of knitted wire, and then compressing the roll or ring to form a compacted knitted-wire element. Knitted-wire elements of this type have been utilized as the core elements for seals, wherein they are covered with fiberglass fabrics for providing reduced leakage rates. Knitted-wire elements of the this type have also been utilized with various types of filler materials to provide reduced leakage rates so that they can then be used for other types of seals or gaskets.
It has been found that these compacted wire seals can be utilized effectively in applications wherein slow gas-leakage rates can be tolerated. In this connection, it has been found that because of the method by which these types of seals are formed, they have substantially reduced leakage rates in comparison with gaskets made from other types of compacted knitted-wire elements. By heating the knitted wire roll or ring in an atmosphere containing oxygen, oxides are produced on the surface of the wire; and when the roll or ring of knitted wire is thereafter compressed, these oxides fill in some of the void areas between the wires in the mesh to reduce the leakage rates of the seal. When the knitted wire seal is formed into a V-shaped configuration, it has sufficient resiliency in the legs of the V-shape to compensate for minor irregularities in the surfaces of elements with which it is engaged or abutted. When the seal is mounted so that a first element is received in engagement with the inner periphery of the seal and a second element is received in engagement with the outer periphery thereof, the V-shape of the seal and the resiliency and flexibility of the compacted wire mesh construction allow it to be maintained in sealing engagement with the first and second elements regardless of irregularities in the surface configurations. The use of the V-shaped cross section thus has advantages when combined with the above-mentioned method is of forming the seal.
One particular application for the above-described seal is in catalytic converters of the type used for treating exhaust gases from internal combustion engines. Most catalytic converters used in this environment comprise a ceramic monolith on which a platinum catalyst is deposited and through which exhaust gases can pass, a refractory or wire-mesh blanket disposed around the ceramic monolith, a metallic housing in which the monolith and the refractory or wire-mesh blanket are mounted, and a seal disposed between the monolith and the housing. The housing of a catalytic converter of this type is constructed for receiving exhaust gases and for directing them so that they pass through the monolith. The refractory or wire-mesh blanket is provided for protecting and cushioning the monolith so that it does not contact the housing and fracture, and the seal of the catalytic converter is provided so that substantial quantities of exhaust gases do not bypass the monolith, although relatively low leak rates can be tolerated.
It has been found that these types of seals can be made economically and that it is particularly effective to use them in catalytic converters. Specifically, the seal of this type, which is preferably made in a V-shaped configuration, can seal between the monolith and the housing of a catalytic converter by compensating for minor irregularities in the configurations of the housing and/or the monolith due to the inherent flexibility of knitted wire mesh. Further, when the seal is constructed from stainless-steel wire it can withstand the very high temperatures which are often experienced in catalytic converters. Because the seal is formed as an endless ring without seams, it is less likely to damage the monolith element of the catalytic converter. When oxides are caused to form on the surface of the wire in the seal (before compaction into a V-shaped configuration) the seal can effectively meet the leak-rate standards for catalytic converters. Even further, since the oxides on the wire of the seal of the instant invention are actually formed from the metal surface of the wire rather than being formed from an additional filler material coated onto the wire surface, the risk that particulate matter will escape from the seal and contaminate or clog downstream components, such as additional catalytic converter elements or monoliths, is substantially reduced.
The seal is preferably formed so that it has a V-shaped configuration wherein the apex of the V-shape thereof is disposed on one side of the seal and the legs of the V-shape diverge from the apex to define interior and exterior surfaces of the seal. The legs of the seal have an angle of divergence of about 60 degrees for substantially the entire length of the seal.
However, a drawback exists with the above described seal in that compacted knitted wire seals with V shaped cross sections tend to become completely nested within each other during packaging and shipping. Seals of this type typically are packaged front to back and then shipped in this configuration; that is, the exterior of one seal engages the interior of an adjacent seal, so they tend to become frictionally engaged during packaging and shipping. As a result, the seals are difficult to separate from each other. Additionally, identifying the edge of one seal from the edge of an adjacent seal is hampered typically because of the textured appearance of the oxidized wire mesh and because the seal is only about 1/4-inch high (with a diameter of about 6 to 20 inches).
Accordingly, two adjacent seals stuck together are often unknowingly assembled into products because the assembler cannot distinguish one seal from another. This accidental assembly of joined seals can create increased pressure on the monolith, causing it to fracture and, eventually, failure of the catalytic converter can occur.